Propeller shaft and propeller shaft production method

Abstract

Apparatus, such as a propeller shaft, includes an outer circumferential portion or outer race to rotate as a unit with an internal shaft (serving as the propeller shaft), an inner circumferential member or inner race to rotate as a unit with an external shaft and a plurality of balls disposed between the outer race and inner race, for transmitting rotation therebetween. A sleeve rotating as a unit with the inner race includes an inside cavity for receiving the external shaft. The sleeve is coated with a coating formed on an inside circumferential surface.

The invention claimed is: 
     
       1. A propeller shaft for transmitting rotation from a drive source of a vehicle to a drive wheel of the vehicle, the propeller shaft comprising:
 a shaft section adapted to be provided between a first shaft on a drive source's side and a second shaft on a drive wheel's side; 
 an outer circumferential portion provided on the shaft section and formed with an inside circumferential surface defining an inside cavity; 
 an inner circumferential member provided in the outer circumferential portion and formed with an inside circumferential surface defining an inside cavity; 
 a plurality of balls provided between the outer circumferential portion and the inner circumferential member; 
 outer engagement grooves which are formed in the inside circumferential surface of the outer circumferential portion in a manner to extend along a rotation axis of the shaft section and which are arranged to receive the balls and thereby to regulate relative rotation between the balls and the outer circumferential portion around the rotation axis of the shaft section; 
 inner engagement grooves which are formed in an outside circumferential surface of the inner circumferential member, and which are arranged to receive the balls and thereby to regulate relative rotation between the balls and the inner circumferential member around the rotation axis of the shaft section; 
 an internally splined portion which is formed in the inside circumferential surface of the inner circumferential member and which is adapted to be engaged with an externally splined portion of a mating shaft which is one of the first shaft and the second shaft; 
 a sleeve receiving portion which is formed in the inner circumferential member on an outward side toward the mating shaft and which is shaped to enlarge the inside cavity of the inner circumferential member so that an inside diameter of the inner circumferential member is greater in the sleeve receiving portion than in a region in which the internally splined portion is formed; 
 a sleeve member including a tubular main portion which extends axially from an outward end to an inward end, and includes an insert portion formed to extend from the inward end toward the outward end and inserted into the sleeve receiving portion of the inner circumferential member and an inside circumferential surface defining an inside cavity into which the mating shaft is to be inserted, the inside circumferential surface of the sleeve member being covered with a coating higher in rust resistance than a material of the tubular main portion; and 
 an annular seal member provided between the sleeve member and the mating shaft, 
 wherein the sleeve member includes an inward side taper portion tapered to decrease an inside diameter of the tubular main portion gradually to an inward end of the insert portion which extends in an inward direction toward the shaft section to the inward end of the insert portion. 
 
     
     
       2. The propeller shaft as claimed in  claim 1 , wherein the insert portion of the tubular main portion of the sleeve member includes a press fit portion fit forcibly in the sleeve receiving portion of the inner circumferential member. 
     
     
       3. The propeller shaft as claimed in  claim 1 , wherein a surface roughness of the coating is smaller than a surface roughness of the tubular main portion. 
     
     
       4. The propeller shaft as claimed in  claim 1 , wherein the sleeve member includes a boot fixing annular groove, formed in an outside circumferential surface of the tubular main portion of the sleeve member, for retaining a boot enclosing an inside space between the outer circumferential portion and the inner circumferential member to prevent entry of a foreign object, and an outward side taper portion tapered to increase the inside diameter of the tubular main portion gradually to an outward end of the tubular main portion which extends along an axis of the sleeve member in an outward direction away from the shaft section to the outward end; and
 wherein the outward side taper portion extends from the outward end of the tubular main portion in the inward direction toward the shaft section, beyond a middle of an axial width of the boot fixing annular groove. 
 
     
     
       5. The propeller shaft as claimed in  claim 1 , wherein the tubular main portion of the sleeve member includes a quenched portion subjected to quenching. 
     
     
       6. The propeller shaft as claimed in  claim 1 , wherein the coating is a covering layer formed by plating. 
     
     
       7. A shaft assembly for transmitting rotation from a drive source of a vehicle to a drive wheel of the vehicle, the shaft assembly comprising:
 the propeller shaft as claimed in  claim 1 ; and 
 the mating shaft, which is connected with the propeller shaft, 
 wherein the mating shaft includes an outside circumferential surface formed with the externally splined portion which is engaged with the internally splined portion of the propeller shaft.